I've scanned and uploaded the Parish Psalter with Chants, edited by Sydney H Nicholson. Nicholson died in 1947 (and all the composers of the chants used in the book died before then), so it's now happily out of copyright.

Because it's a big volume (236 pages), I've had to split it up into five PDFs to stay beneath the 16MB filesize limit while retaining acceptable quality.

I've created a works page, but this only has the first part on it. I've uploaded the remaining four parts, but couldn't readily see how to add them to the works page while still giving them CPDL numbers. Would one of the admins be able to fix this?

The copyright's pretty straightforward - Nicholson died in 1947 so the copyright expired at the end of 2017 in the UK (Copyright, Designs & Patents Act I.12.2). The scanned edition is from 1932 (reprinted 1943) so any typographical copyright has long since expired. I've checked the death dates of the composers of the individual chants in Humphreys and Evans' 'Dictionary of Composers for the Church in Great Britain and Ireland' and they're all long pre-1947.

Apparently no copyright renewal occurred after 28 years from publication: I found nothing in the US Catalogue of Copyright Entries. It is probably public domain then. The copyright review process performed at IMSLP seems to agree on this. I'm one of the IMSLP copyright reviewers, however this score was not reviewed by me, so my own search in the US Catalogue of Copyright Entries is completely independent.